In the process of removing a hall closet and adding a bedroom closet, I have removed and added some framing. I now have a couple of sections where I have new drywall meeting existing drywall (that has a few coats of paint). This occurs along inside corners as well as butted joints.

My question is how do I join the two? Just treat like a normal taping job with all new drywall? How is the bond of joint compound to paint?

Thanks for your suggestions and comments.

 

Joint compound seems to stick to flat and semi gloss pirety good.
To give you a smooth lock i would lightly sand the existing paint then tape like normal and repaint.